000 WTNT44 KNHC 270250 TCDAT4 TROPICAL STORM ISAAC DISCUSSION NUMBER 24 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012 1100 PM EDT SUN AUG 26 2012 SATELLITE IMAGERY HAS SHOWN AN INCREASE IN THE AREA OF COLD CLOUD TOPS NEAR THE CENTER OF ISAAC. HOWEVER...THERE HAS NOT BEEN ANY SIGNIFICANT CHANGE IN ORGANIZATION IN RADAR DATA FROM KEY WEST THIS EVENING. IN FACT...THE AIRCRAFT FIXES HAVE BEEN NEAR THE SOUTHEASTERN EDGE OF THE CONVECTIVE CLUSTER SEEN IN BOTH SATELLITE AND RADAR IMAGERY. AN EARLIER SHIP OBSERVATION AND SFMR MEASUREMENTS OF 50-55 KT SUPPORTED INCREASING THE INTENSITY TO 55 KT ON THE INTERMEDIATE ADVISORY. SINCE THAT TIME...THE AIRCRAFT HAS NOT FOUND ANY STRONGER WINDS SO THE INITIAL WIND SPEED REMAINS UNCHANGED. THE LARGE SCALE ENVIRONMENTAL FACTORS...WARM WATERS...AND A CONDUCIVE UPPER-AIR PATTERN FAVOR STRENGTHENING DURING THE NEXT COUPLE OF DAYS. HOWEVER...THE LACK OF AN INNER CORE AND LARGE WIND FIELD COULD CONTINUE TO BE IMPEDING FACTORS FOR SIGNIFICANT STRENGTHENING IN THE SHORT TERM. THE NHC INTENSITY FORECAST SHOWS A GRADUAL INCREASE IN WIND SPEED DURING THE NEXT 12 HOURS OR SO...FOLLOWED BY MORE STEADY STRENGTHENING. THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS/LGEM GUIDANCE AND THE INTENSITY CONSENSUS. AIRCRAFT AND RADAR CENTER FIXES INDICATE THAT ISAAC JOGGED WESTWARD AND SLOWED DOWN THIS EVENING. HOWEVER...THE LONGER TERM MOTION IS 285/12 KT. THE MODELS SHOW ISAAC TURNING TOWARD THE NORTHWEST INTO A BREAK IN THE SUBTROPICAL RIDGE. ALTHOUGH THE MODELS AGREE ON THIS TURN...THERE IS AN UNUSUALLY LARGE SPREAD IN THE TRACK GUIDANCE AFTER 24 HOURS. THE SPREAD OF LANDFALL LOCATIONS ALONG THE NORTHERN GULF COAST RANGES FROM THE TEXAS/LOUISIANA BORDER EASTWARD TO THE ALABAMA/FLORIDA BORDER WITH THE HWRF...GFDL...AND GFS NEAR THE WESTERN EDGE AND THE UKMET AND ECMWF ALONG THE EASTERN EDGE OF THE ENVELOPE. OVERALL...THE CONSENSUS HAS SHIFTED A LITTLE WESTWARD AND THE OFFICIAL FORECAST AS BEEN MOVED IN THAT DIRECTION. THE NHC FORECAST IS BETWEEN THE ECMWF AND GFS ENSEMBLE MEANS AND NEAR THE HFIP MULTI-MODEL CONSENSUS. BECAUSE OF THE VERY LARGE SPREAD IN THE GUIDANCE...THERE CONTINUES TO BE GREATER THAN USUAL TRACK FORECAST UNCERTAINTY. THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK DUE TO FORECAST UNCERTAINTIES AND THE FACT THAT SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 24.2N 82.9W 55 KT 65 MPH 12H 27/1200Z 25.2N 84.8W 60 KT 70 MPH 24H 28/0000Z 26.5N 86.7W 70 KT 80 MPH 36H 28/1200Z 27.9N 88.3W 80 KT 90 MPH 48H 29/0000Z 28.9N 89.3W 85 KT 100 MPH 72H 30/0000Z 30.6N 90.3W 70 KT 80 MPH...INLAND 96H 31/0000Z 33.0N 91.0W 30 KT 35 MPH...INLAND 120H 01/0000Z 36.0N 91.0W 20 KT 25 MPH...INLAND $$ FORECASTER BROWN